Currently when .llvm.call-graph-profile is created by llvm it explicitly encodes the symbol indices. This section is basically a black box for post processing tools. For example, if we run strip -s on the object files the symbol table changes, but indices in that section do not. In non-visible behavior indices point to wrong symbols. The visible behavior indices point outside of Symbol table: "invalid symbol index".
This patch changes the format by using R_*_NONE relocations to indicate the from/to symbols. The Frequency (Weight) will still be in the .llvm.call-graph-profile, but symbol information will be in relocation section. In LLD information from both sections is used to reconstruct call graph profile. Relocations themselves will never be applied.
With this approach post processing tools that handle relocations correctly work for this section also. Tools can add/remove symbols and as long as they handle relocation sections with this approach information stays correct.
Doing a quick experiment with clang-13.
The size went up from 107KB to 322KB, aggregate of all the input sections. Size of clang-13 binary is ~118MB. For users of -fprofile-use/-fprofile-sample-use the size of object files will go up slightly, it will not impact final binary size.
Reviewed By: jhenderson, MaskRay
Differential Revision: https://reviews.llvm.org/D104080
This patch adds support for a new field in the FileHeader, which states
the name to use for the section header string table. This also allows
combining the string table with another string table in the object, e.g.
the symbol name string table. The field is optional. By default,
.shstrtab will continue to be used.
This partially fixes https://bugs.llvm.org/show_bug.cgi?id=50506.
Reviewed by: Higuoxing
Differential Revision: https://reviews.llvm.org/D104035
There was an off-by-one error caused by an index (which included an
index for the null section header) being used to check against the size
of a list of sections (which didn't include the null section header).
This is a partial fix for https://bugs.llvm.org/show_bug.cgi?id=50506.
Reviewed by: MaskRay
Differential Revision: https://reviews.llvm.org/D104098
As discussed in D95511, this allows us to encode invalid BBAddrMap
sections to be used in more rigorous testing.
Reviewed By: jhenderson
Differential Revision: https://reviews.llvm.org/D96831
As discussed in D95511, this allows us to encode invalid BBAddrMap
sections to be used in more rigorous testing.
Reviewed By: jhenderson
Differential Revision: https://reviews.llvm.org/D96831
Currently we don't allow the following definition:
```
Sections:
- Type: SectionHeaderTable
- Name: .foo
Type: SHT_PROGBITS
```
We report an error: "SectionHeaderTable can't be empty. Use 'NoHeaders' key to drop the section header table".
It was implemented in this way earlier, when `SectionHeaderTable`
was a dedicated key outside of the `Sections` list. And we did not
allow to select where the table is written.
Currently it makes sense to allow it, because a user might
want to place the default section header table at an arbitrary position,
e.g. before other sections. In this case it is not convenient and error prone
to require specifying all sections:
```
Sections:
- Type: SectionHeaderTable
Sections:
- Name: .foo
- Name: .strtab
- Name: .shstrtab
- Name: .foo
Type: SHT_PROGBITS
```
This patch allows empty SectionHeaderTable definitions.
Differential revision: https://reviews.llvm.org/D95341
We already set the `sh_entsize` field in a single place
for all non-implicit sections.
This patch reorders the logic slightly and with it
we finally have the only one place where the `sh_entsize` is set.
obj2yaml will not dump the `EntSize` key for `SHT_DYNSYM/SHT_SYMTAB` sections anymore,
when the value of `sh_entsize` is equal to `sizeof(Elf_Sym)`
Note that this also seems revealed an issue in llvm-objcopy:
Previously yaml2obj set the `sh_entsize` for the `.symtab` section to 0x18,
now we it sets it for `SHT_SYMTAB` sections, i.e. by type.
But the `llvm-objcopy/ELF/only-keep-debug.test` has a `.symtab` section of type `SHT_STRTAB`,
and now yaml2obj sets the `sh_entsize` to 0 for it.
I had to update the corresponding check lines for `ES`, but the behavior of
`llvm-objcopy` should be fixed instead I think.
I've added a TODO and a comment.
Differential revision: https://reviews.llvm.org/D95364
This refactors the logic that sets the `sh_link` field.
With this patch we set it in a single place for all sections.
Differential revision: https://reviews.llvm.org/D95354
This was discussed in D93678 thread.
Currently we have one special chunk - Fill.
This patch re implements the "SectionHeaderTable" key to become a special chunk too.
With that we are able to place the section header table at any location,
just like we place sections.
Differential revision: https://reviews.llvm.org/D95140
This makes the following improvements.
For `SHT_GNU_versym`:
* yaml2obj: set `sh_link` to index of `.dynsym` section automatically.
For `SHT_GNU_verdef`:
* yaml2obj: set `sh_link` to index of `.dynstr` section automatically.
* yaml2obj: set `sh_info` field automatically.
* obj2yaml: don't dump the `Info` field when its value matches the number of version definitions.
For `SHT_GNU_verneed`:
* yaml2obj: set `sh_link` to index of `.dynstr` section automatically.
* yaml2obj: set `sh_info` field automatically.
* obj2yaml: don't dump the `Info` field when its value matches the number of version dependencies.
Also, simplifies few test cases.
Differential revision: https://reviews.llvm.org/D94956
This reuses the code from yaml2obj (moves it to ELFYAML.h).
With it we can set the `sh_entsize` in a single place in `obj2yaml`.
Note that it also fixes a bug of `yaml2obj`: we do not
set the `sh_entsize` field for the `SHT_ARM_EXIDX` section properly.
Differential revision: https://reviews.llvm.org/D93858
We have the following issues related to group sections:
1) yaml2obj is unable to set the custom `sh_entsize` value, because the `EntSize`
key is currently ignored.
2) obj2yaml is unable to dump the group section which `sh_entsize != 4`.
3) obj2yaml always dumps the "EntSize" for group sections, though
usually we are trying to omit dumping default values when dumping keys.
I.e. we should not print the "EntSize" key when `sh_entsize` == 4.
This patch fixes (1),(3) and adds the test case to document the behavior of (2).
Differential revision: https://reviews.llvm.org/D93854
When a field is optional we can use the `=<none>` syntax in macros.
This patch makes `Value`/`Size` fields of `Symbol` optional
and adds test cases for them.
Differential revision: https://reviews.llvm.org/D93010
This is similar to what we did earlier for fields of the Section class.
When a field is optional we can use the =<none> syntax in macros.
This was splitted from D92478.
Differential revision: https://reviews.llvm.org/D92565
Currently we never dump the `sh_offset` key.
Though it sometimes an important information.
To reduce the noise this patch implements the following logic:
1) The "Offset" key for the first section is always emitted.
2) If we can derive the offset for a next section naturally,
then the "Offset" key is omitted.
By "naturally" I mean that section[X] offset is expected to be:
```
offsetOf(section[X]) == alignTo(section[X - 1].sh_offset + section[X - 1].sh_size, section[X].sh_addralign)
```
So, when it has the expected value, we omit it from the output.
Differential revision: https://reviews.llvm.org/D91152
Imagine we have a YAML declaration of few sections: `foo1`, `<unnamed 2>`, `foo3`, `foo4`.
To put them into segment we can do (1*):
```
Sections:
- Section: foo1
- Section: foo4
```
or we can use (2*):
```
Sections:
- Section: foo1
- Section: foo3
- Section: foo4
```
or (3*) :
```
Sections:
- Section: foo1
## "(index 2)" here is a name that we automatically created for a unnamed section.
- Section: (index 2)
- Section: foo3
- Section: foo4
```
It looks really confusing that we don't have to list all of sections.
At first I've tried to make this rule stricter and report an error when there is a gap
(i.e. when a section is included into segment, but not listed explicitly).
This did not work perfect, because such approach conflicts with unnamed sections/fills (see (3*)).
This patch drops "Sections" key and introduces 2 keys instead: `FirstSec` and `LastSec`.
Both are optional.
Differential revision: https://reviews.llvm.org/D90458
YAML support allows us to better test the feature in the subsequent patches. The implementation is quite similar to the .stack_sizes section.
Reviewed By: jhenderson, grimar
Differential Revision: https://reviews.llvm.org/D88717
These sections are implicit and handled a bit differently.
Currently the "Offset" is ignored for them.
This patch fixes an issue.
Differential revision: https://reviews.llvm.org/D90446
`Link` is not an optional field currently.
Because of this it is not convenient to write macros.
This makes it optional and fixes corresponding test cases.
Differential revision: https://reviews.llvm.org/D90390
When `NoHeaders` is set, we still have following issues:
1) We emit the `.shstrtab` implicit section of size 1 (empty string table).
2) We still align the start of the section header table, what affects the output size.
3) We still write section header table bytes.
This patch fixes all of these issues.
Differential revision: https://reviews.llvm.org/D90295
Our "implicit" sections are handled separately from regular ones.
It turns out that the "Offset" key is not handled properly for them.
Perhaps we can generalize handling in one place, but before doing that I'd like
to add support and test cases for each implicit section.
(I need this particular single change to unblock another patch that is already on review,
and I guess doing it independently for each section will be cleaner, see below).
In this patch I've removed `explicit-dynsym-no-dynstr.yaml` to `dynsym-section.yaml`
and added the new test into. In a follow-up we probably might want
to merge 2 another existent `dynsymtab-*.yaml` tests into it too.
Differential revision: https://reviews.llvm.org/D90224
Imagine the following declaration of a section:
```
Sections:
- Name: .dynsym
Type: SHT_DYNSYM
AddressAlign: 0x1111111111111111
```
The aligment is large and yaml2obj reports an error currently:
"the desired output size is greater than permitted. Use the --max-size option to change the limit"
This patch implements the "ShAddrAlign" key, which is similar to other "Sh*" keys we have.
With it it is possible to override the `sh_addralign` field, ignoring the writing of alignment bytes.
Differential revision: https://reviews.llvm.org/D90019
This is a follow-up for D89039 patch, which adds a support for
`Content`/`Size` for all sections.
Assuming that all of sections have a support of these 2 fields,
we can simplify and generalize the code.
Depends on D89039
Differential revision: https://reviews.llvm.org/D89120
Currently we have a few sections that
does not support specifying no keys for them. E.g. it is required that one
of "Content", "Size" or "Entries" key is present. There is no reason to
have this restriction. We can allow this and emit an empty section instead.
This opens road for a simplification and generalization of the code in `validate()`
that is discussed in the D89039 thread.
Depends on D89039.
Differential revision: https://reviews.llvm.org/D89391
Many sections either do not have a support of `Size`/`Content` or support just a
one of them, e.g only `Content`.
`Section` is the base class for sections. This patch adds `Content` and `Size` members
to it and removes similar members from derived classes. This allows to cleanup and
generalize the code and adds a support of these keys for all sections (`SHT_MIPS_ABIFLAGS`
is a only exception, it requires unrelated specific changes to be done).
I had to update/add many tests to test the new functionality properly.
Differential revision: https://reviews.llvm.org/D89039
The `Group` class represents a group section and it is
named inconsistently with other sections which all has
the "Section" suffix. It is sometimes confusing,
this patch addresses the issue.
Differential revision: https://reviews.llvm.org/D88892
Specification for SHT_HASH table says (https://refspecs.linuxbase.org/elf/gabi4+/ch5.dynamic.html#hash)
that it contains Elf32_Word entries for both 32/64 bit objects.
Currently both GNU linkers and LLD sets the `sh_entsize` field to `4`.
At the same time, `yaml2obj` ignores the `EntSize` field for SHT_HASH sections.
This patch fixes this and also adds a support for obj2yaml: it will not
dump this field when the `sh_entsize` contains the default value (`4`).
Differential revision: https://reviews.llvm.org/D88652
This patch adds support for referencing different abbrev tables. We use
'ID' to distinguish abbrev tables and use 'AbbrevTableID' to explicitly
assign an abbrev table to compilation units.
The syntax is:
```
debug_abbrev:
- ID: 0
Table:
...
- ID: 1
Table:
...
debug_info:
- ...
AbbrevTableID: 1 ## Reference the second abbrev table.
- ...
AbbrevTableID: 0 ## Reference the first abbrev table.
```
Reviewed By: jhenderson
Differential Revision: https://reviews.llvm.org/D83116
Currently we have to set 'Machine' to something in our
YAML descriptions. Usually we use 'EM_X86_64' for 64-bit targets
and 'EM_386' for 32-bit targets. At the same time, in fact, in most
cases our tests do not need a machine type and we can use
'EM_NONE'.
This is cleaner, because avoids the need of using a particular machine.
In this patch I've made the 'Machine' key optional (the default value,
when it is not specified is `EM_NONE`) and removed it (where possible)
from yaml2obj, obj2yaml and llvm-readobj tests.
There are few tests left where I decided not to remove it, because
I didn't want to touch CHECK lines or doing anything more complex
than a removing a "Machine: *" line and formatting lines around.
Differential revision: https://reviews.llvm.org/D86202
In this patch, we add a helper function getDWARFEmitterByName(). This
function returns the proper DWARF section emitting method by the name.
Reviewed By: jhenderson
Differential Revision: https://reviews.llvm.org/D84952
In this patch, emitDebugPubnames(), emitDebugPubtypes(),
emitDebugGNUPubnames(), emitDebugGNUPubtypes() are added.
Reviewed By: jhenderson
Differential Revision: https://reviews.llvm.org/D85003
This adds the `ShType` key similar to others `Sh*` keys we have.
My use case is the following. Imagine we have a `SHT_SYMTAB_SHNDX`
section and want to hide it from a dumper. The natural way would be to
do something like:
```
- Name: .symtab_shndx
Type: [[TYPE=SHT_SYMTAB_SHNDX]]
Entries: [ 0, 1 ]
```
and then change the TYPE from `SHT_SYMTAB_SHNDX` to something else,
for example to `SHT_PROGBITS`.
But we have a problem: regular sections does not have `Entries` key,
so yaml2obj will be unable to produce a section.
The solution is to introduce a `ShType` key to override the final type.
This is not the first time I am facing the need to change the type. I
was able to invent workarounds or solved issues differently in the past,
but finally came to conclusion that we just should support the `ShType`.
Differential revision: https://reviews.llvm.org/D84738
This patch implements the .debug_rnglists section. We are able to
produce the .debug_rnglists section by the following syntax.
```
debug_rnglists:
- Format: DWARF32 ## Optional
Length: 0x1234 ## Optional
Version: 5 ## Optional
AddressSize: 0x08 ## Optional
SegmentSelectorSize: 0x00 ## Optional
OffsetEntryCount: 2 ## Optional
Offsets: [1, 2] ## Optional
Lists:
- Entries:
- Operator: DW_RLE_base_address
Values: [ 0x1234 ]
```
The generated .debug_rnglists is verified by llvm-dwarfdump, except for
the operator DW_RLE_startx_endx, since llvm-dwarfdump doesn't support
it.
Reviewed By: jhenderson
Differential Revision: https://reviews.llvm.org/D83624
This patch helps add support for emitting the .debug_str_offsets section
to yaml2elf.
Reviewed By: jhenderson, MaskRay
Differential Revision: https://reviews.llvm.org/D83853
When setting the NoHeaders to false,
the e_shnum field wasn't set correctly.
This patch fixes this bug.
Differential revision: https://reviews.llvm.org/D83941
In D83482 we agreed to name e_* fields that are used for overriding
values (like e_phoff) as EPh* (e.g. EPhOff).
Currently we have a set of e_sh* fields that are named inconsistently
with this rule. This patch renames all of them.
Differential revision: https://reviews.llvm.org/D83766
Imagine we have an YAML description for some object and we want to
produce 2 outputs: with and without the section header.
A natural way to do it would look like:
```
--- !ELF
FileHeader:
Class: ELFCLASS64
Data: ELFDATA2LSB
Type: ET_REL
Machine: EM_X86_64
Sections:
...
SectionHeaderTable:
NoHeaders: [[NOHEADERS]]
```
But currently, we do not distinguish between no `NoHeaders` key case
and `NoHeaders == false`. Because of this we can't simply specify
`NOHEADERS = false`, as tool starts to complain.
With this patch the behavior changed. When we have:
```
SectionHeaderTable:
NoHeaders: false
```
it is the same as we have no `SectionHeaderTable` at all.
(`NoHeaders` key still can't be used with `Sections/Excluded` keys)
Differential revision: https://reviews.llvm.org/D83672
This adds `EPhOff`, `EPhEntSize` and `EPhNum` keys.
Will be useful for creating broken objects for testing llvm-readelf.
Differential revision: https://reviews.llvm.org/D83482
This patch helps add support for emitting the .debug_gnu_pubnames and .debug_gnu_pubtypes sections.
The .debug_gnu_pub* sections is verified by llvm-dwarfdump.
Known issues:
- Doesn't support emitting multiple pub-tables.
Reviewed By: jhenderson
Differential Revision: https://reviews.llvm.org/D82367
This patch helps add support for emitting the .debug_pubnames section to yaml2elf.
Known issues:
- Current implementation doesn't support emitting multiple sets of entries.
- Doesn't support DWARF64.
Reviewed By: jhenderson
Differential Revision: https://reviews.llvm.org/D82296
This patch helps add support for emitting the .debug_info section to yaml2elf.
Reviewed By: jhenderson, grimar, MaskRay
Differential Revision: https://reviews.llvm.org/D82073
This patch enables yaml2elf emit the .debug_abbrev section.
The generated .debug_abbrev is verified using `llvm-dwarfdump`.
Known issues that will be addressed later:
- Current implementation doesn't support generating multiple abbreviation tables in one .debug_abbrev section.
Reviewed By: jhenderson, grimar
Differential Revision: https://reviews.llvm.org/D81820
